Rocketman kindly requested I post these comments after I reviewed his materials.
Thank you for the material. It is useful.
I am preparing a thorough set of commentary that I would like to share with you. Here are my initial thoughts.
1. I think that small bores will be a problem. As you know, 20s and 28s often were considered ladies or children's guns, or as Watson Bros., for example seem to specialize in the small bores, and not just for children or ladies.
However, there was a move to make the 16 bore an alternative to the 12 bore especially when the trend came to shooting lighter weight guns beginning just before the first world war, when Nitro powders finally came into their own. For example, Beesley made a specialty, as did Churchill, of bringing to the market 16 bore game guns as an alternative to lightweight 12 bores. For example, I own a Beesley best 16 SLE that was built around 1908 that is about a nice a gun you can possibly find - it's number two of a pair. (Another move at that time was the 2 inch 12 bore which I personally think was a mistake. A late friend of mine owned a Churchill Premier 2 inch that was a gorgeous gun though.) My point is that pairs of best 16 bores or single guns with long stocks might be perhaps in their own category, as would be for example 28 bores with long stocks. Last, I checked, Purdey's made approximately 5XX 28 bores over the years. How many of these guns were guns with long stocks? How many these guns were best quality Beesley action guns? For the purposes of shooting, obviously, a long stock H&H Royal Assisted opener or Purdey Beesley actioned 28 bore is going to be a very desirable commodity. Is the .410 as desirable?
2. This brings me to the next very important topic. How well were the guns finished? Now we all know that Purdey, for example, prides itself on the finish that it gives guns, and rightfully so. It's probably the standard of finish by which all other guns can be judged. There are exceptions to that of course, during early 60s the finish of many British guns went downhill, with a few exceptions. (Crossedchisels can correct me on this.) Of course the pundits will reject ANY gun from this era rather than believing their eyes or their gunmaker....So, the adage that you judge the gun by its inherent quality is still a good one. But I do think that Purdey's, best grade Churchill boxlocks and sidelocks, best grade Beesley's are among some of the best finished guns that you can possibly find. Often to ascertain this you actually have to take the gun apart and see how the gun was finished inside. And of course, there are individuals, like Nelson and Adam Davies, who build a few guns for the discerning and their guns are top shelf by any standard.
However, there are exceptions to this. I own a Churchill Imperial that was engraved, to the best of my knowledge, by Harry Kell. The engraving compared to other Imperial's I have seen is absolutely exquisite. I own a CS Rosson that although built probably by Wrights in Birmingham is London proofed, and as far as we can tell, was probably engraved by Sumner in a style very close to Boss rose and scroll in execution if not design. So the point is that even some second quality guns from (Best) Makers were often finished to a higher standard by the same people who finished the Best guns. My point - these are guns to look for if you want a good deal with pride of ownership.
3.The bottom line is that I suggest you add a fourth column of rating to your Excel spreadheet which is a “standard of finish” and that this standard should apply to their best guns only. That way you're comparing apples to apples. I think this would also help you differentiate between some of the smaller Birmingham, and/or provincial maker's guns, who did MUCH more than just take a Scott gun and have their name put on. That way people could have their eyes out for what I call a sleeper. It would take me some time to go through your list and make some suggestions about some of these guns that I felt were finished to a much higher standard than the average Birmingham or provincial gun. Please realize I would only do this for guns that I have seen several examples of; as Aristotle says “one swallow does not a summer make.” For example I would rate CS Rosson, as being higher on both the innovation and finish scale then you have it rated. Both Rosson's and Churchill were among the first to used the Smith's assisted opening principal for their best guns.
So I (and I am sure others) will be happy to go through the list and rate some of the guns for innovation in and quality of finish based on their experience. (Please, don't give me this silliness about Spanish Bests and so on - that's merely a journalistic device designed to sell books and guns.)
So, "standard of finish" should be added, I think we agree.